Physics Mock Test- 1 - Class 10 MCQ

• The focal length of a lens indicates how it converges or diverges light.
• A positive focal length, like +12 cm, means the lens is a convex lens.
• Convex lenses converge light rays to a point, forming real or virtual images.
• In contrast, concave lenses have a negative focal length and diverge light, forming virtual images only.
• Thus, a lens with a focal length of +12 cm is definitively a convex lens.

• The focal length of a lens indicates its type.
• A concave lens has a negative focal length.
• A convex lens has a positive focal length.
• Since the given focal length is -12 cm, it indicates a concave lens.
• Concave lenses diverge light rays, while convex lenses converge them.
• Therefore, the correct answer is option 1: Concave lens.

Potential difference is the difference in electric potential energy between two points.
It is the amount of work done in moving a unit positive charge from one point to another point in an electric field. This is measured in volt. 

Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge.

Electric power in terms of current = IR2 and in terms of voltage = V2/R and in terms of voltage and current both = VI

• Increase in length: When the length of a conductor increases, the resistance also increases because the electrons have to travel a longer distance, resulting in more collisions with atoms in the conductor.



• Increase in volume: Increasing the volume of a conductor does not necessarily increase the resistance. Resistance depends on the material of the conductor and its dimensions, but volume alone does not directly affect resistance.



• Decrease in area: If the cross-sectional area of a conductor decreases, the resistance increases. This is because there is less space for the electrons to flow, leading to more collisions and increased resistance.



• Therefore, the resistance of a conductor increases with factors like an increase in length or decrease in area, as mentioned in options I and III.



• Option A, which states "I or III", is the correct answer as it includes the correct factors affecting the resistance of a conductor.

For a spherical mirror focal length is one half of its radius of curvature i.e. f = R/2 or R = 2f

The incident ray coming from the object placed at infinity will be parallel to the principal axis. When the parallel beam of light incident on a mirror or lens, irrespective of their nature, after reflection/refraction, will pass or appear to pass through their principal focus. Hence highly diminished and point size image will be formed at their focus.

Red colour has a longer wavelength, which means it is scattered the least by smoke or fog. This characteristic makes it more visible from a distance.

Range of vision for a normal human eye is between its near point and far point i.e, from 25cm to infinity.

An electric current is said to exist when there is a net flow of electric charge through a region. In electric circuits this charge is often carried by electrons moving through a wire.

Conventional current or simply current, behaves as if positive charge carriers cause current to flow. Conventional current flows from the positive terminal to the negative.

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

• Convex Lens: A magnifying glass is made up of a convex lens. A convex lens is thicker in the middle and thinner at the edges. It converges light rays to a focal point, creating a magnified image of the object being viewed.


• Function: When an object is placed close to a convex lens, it forms a virtual and magnified image on the same side of the lens as the object. This is why a convex lens is used in magnifying glasses to make objects appear larger when viewed through the lens.


• Optical Properties: Convex lenses are also known as converging lenses because they converge light rays. This convergence of light rays allows the magnifying glass to magnify the object being observed.


• Use: The convex lens of a magnifying glass is commonly used for tasks such as reading small print, examining small details, or conducting scientific experiments that require magnification.

Reasons for the melting point of fuse wire being low:

• Protection: The main purpose of a fuse wire is to protect electrical circuits from damage due to overcurrent. A low melting point ensures that the fuse wire will melt quickly when there is excess current flowing through the circuit, breaking the circuit and preventing damage.


• Safety: A low melting point ensures that the fuse wire will melt before any other components in the circuit are damaged. This helps in preventing fires and other hazards that may arise due to overcurrent.


• Efficiency: A fuse wire with a low melting point reacts quickly to overcurrent situations, allowing for the circuit to be interrupted promptly. This helps in maintaining the efficiency of the electrical system and preventing any further damage.


• Ease of Replacement: A fuse wire with a low melting point is easy to replace once it has melted. This ensures that the circuit can be restored quickly, minimizing downtime.

• High powered electric appliances draw a significant amount of current, which can lead to overheating of the wires.


• Inferior wires are not designed to handle high electrical currents and can easily overheat, potentially causing a fire hazard.


• Not being earthed means that there is no proper way to redirect excess current in case of a short circuit, increasing the risk of electric shock and fire.

• Using inferior wires in a high powered electric appliance without proper grounding poses a serious hazard to both property and life.


• There is a high risk of fire due to overheating of the wires, which can quickly escalate and cause extensive damage.


• The lack of grounding increases the risk of electric shock, which can be fatal in severe cases.

• Given the combination of inferior wires and lack of grounding in a high powered electric appliance, the situation is classified as a hazard.


• Immediate action should be taken to either replace the wires with high-quality ones and ensure proper grounding or discontinue the use of the appliance to prevent any potential accidents.

The field consists of concentric circles centred on the wire.
On applying right-hand thumb rule, we find the direction of magnetic field. The field is in the form of concentric circles centred on the wire carrying current.
Hence, the option (d) is correct.

At noon, the sun is at top and the light rays coming from the sun have to travel lens distance hence, all colours get scattered very less even blue and violet.

A student, who cannot read words written on blackboard from the last bench of his class room, is suffering from the myopia or short-sightedness defect of vision of eye.

A "grounding" wire on the other hand is a safety wire that has intentionally been connected to earth. The grounding wire does not carry electricity under normal circuit operations. It's purpose is to carry electrical current only under short circuit or other conditions that would be potentially dangerous.

Fleming’s right-hand rule gives the direction of induced current in a rectangular coil when the coil is rotated in a uniform magnetic field.

The current described in the question alternates its direction periodically, which is characteristic of alternating current (AC). This distinguishes it from:

• Direct current (DC), which flows in one direction.
• Pulsating current, which varies in magnitude without reversing direction.

Virtual objects can form a real image in a concave mirror. Concave mirrors do not form virtual images of real objects.

When a soft iron bar is introduced inside a current carrying solenoid, the magnetic field inside the solenoid will increase.

Person cannot see distant objects clearly. So he is suffering from myopia. The defect is corrected by using concave lens of power

A student sitting on the last bench of class can read the letters written on the blackboard. It means his farsight is normal. However, he cannot read the letters written in his textbook distinctly. It means he is suffering from long-sightedness (hypermetropia) and the near point of his eye has receded away

Objects are not visible through the fog because droplets scatter the light rays.